Auditory Brainstem Responses will be studied in both normal subjects and patients with diseases of the central nervous system as a way of objectively measuring brainstem function regulating human hearing. The responses consist of a sequence of seven potentials during the 10 msec following a click. They can be detected with scalp electrodes using computer averaging techniques and represent the far-field reflection of electrical events taking place within the brainstem structures comprising the auditory pathway. This work will define the normal parameters of latency and amplitude of the response components as a function of signal intensity and subject age. We will examine the usefulness of the response measures in the clinical situation as a diagnostic aid in lesions of both the central nervous system and peripheral auditory structures. The neuroanatomical mechanisms underlying the genesis of the various response components will be analyzed in animal studies using stereotoxic lesions of various auditory structures. The project plans to use current knowledge of the physiology and anatomy of the auditory system to problems of neurological disease. BIBLIOGRAPHIC REFERENCES: Starr, A. and Achor, J. Auditory Brainstem Response in Neurological Disease. Archives of Neurology, 761-768, 1975. Starr, A. Clinical Relevance of Auditory Brainstem Responses. In: Evoked Responses, J.E. Desmedt (Ed.), 1976, in press.